The 1956 book by W. Ross Ashby called INTRODUCTION TO CYBERNETEICS introduced the phrase Law of Requisite Variety. It is sometimes called Ashby's Law. Basically it is meant to illustrate that that variety is required to regulate variety. You have stated a rather common misunderstanding of that principle quite explicitly is saying "The system (or therapist) with the most choices is the most successful." People are not separate from the system in which they find themselves and therapy is a cooperative not a competitive situation. While it is indeed helpful to have a great number of choices, the person (client or therapist) who begins to characterize experience in terms of a past life has most certainly run out of choices having to do with describing and making useful sense out of behavior.